This invention relates to thermosettable resin compositions. The invention further relates to the preparation of polymers from a new class of homopolymerizable and copolymerizable monomers. In one aspect, the invention relates to the preparation of low dielectric constant thermosettable resins.
Thermosettable resins are used in applications, such as advanced aerospace composites, requiring good high-temperature properties, including high (above 200.degree. C.) cured glass transition temperature and toughness, as reflected in Mode I fracture toughness values above about 2 MPa-m.sup.1/2. Examples of thermosettable resins useful in advanced composites include epoxy resins and bismaleimide resins. Epoxy resins have good processing properties but relatively low glass transition temperatures. Bismaleimide resins have superior high-temperature properties but are very brittle. Standard toughening modifiers for bismaleimides, such as diallylbisphenol-A, generally do not give fracture toughness values greater than about 1 MPa-m.sup.1/2 when copolymerized with bismaleimides, and attaining even this degree of toughness often requires the use of so much modifier that the Tg of the cured product is lowered considerably.
Bisbenzocyclobutene monomers can be copolymerized with bismaleimides, as described in U.S. Pat. No. 4,973,636, to provide cured materials having high Tg and high Mode I fracture toughness. However, such bisbenzocyclobutene monomers are quite expensive to prepare, requiring multistep syntheses from the nearest commercially-available material. The cost of the monomer precludes these polymers from practical application in most end-uses.
It is thus an object of the invention to provide new thermoset resin materials. In one aspect, it is an object of the invention to provide polymeric materials having good toughness and low dielectric constant.